electronics Article Theoretical and Experimental Substractions of Device Temperature Determination Utilizing I-V Characterization Applied on AlGaN/GaN HEMT Martin Floroviˇ c 1, * , Jaroslav Ková ˇ c, Jr. 1 , Aleš Chvála 1 , Jaroslav Ková ˇ c 1 , Jean-Claude Jacquet 2 and Sylvain Laurent Delage 2   Citation: Floroviˇ c, M.; Kovᡠc, J., Jr.; Chvála, A.; Kovᡠc, J.; Jacquet, J.-C.; Delage, S.L. Theoretical and Experimental Substractions of Device Temperature Determination Utilizing I-V Characterization Applied on AlGaN/GaN HEMT. Electronics 2021, 10, 2738. https://doi.org/ 10.3390/electronics10222738 Academic Editor: Alessandro Gabrielli Received: 14 October 2021 Accepted: 4 November 2021 Published: 10 November 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 812 19 Bratislava, Slovakia; jaroslav_kovac@stuba.sk (J.K.J.); ales.chvala@stuba.sk (A.C.); jaroslav.kovac@stuba.sk (J.K.) 2 III-V Lab, Route de Nozay, 91460 Marcoussis, France; jean-claude.jacquet@3-5lab.fr (J.-C.J.); sylvain.delage@3-5lab.fr (S.L.D.) * Correspondence: martin.florovic@stuba.sk Abstract: A differential analysis of electrical attributes, including the temperature profile and trap- ping phenomena is introduced using a device analytical spatial electrical model. The resultant current difference caused by the applied voltage variation is divided into isothermal and thermal sections, corresponding to the instantaneous time- or temperature-dependent change. The average tempera- ture relevance is explained in the theoretical section with respect to the thermal profile and major parameters of the device at the operating point. An ambient temperature variation method has been used to determine device average temperature under quasi-static state and pulse operation, was com- pared with respect to the threshold voltage shift of a high-electron-mobility transistor (HEMT). The experimental sections presents theoretical subtractions of average channel temperature determination including trapping phenomena adapted for the AlGaN/GaN HEMT. The theoretical results found using the analytical model, allow for the consolidation of specific methodologies for further research to determine the device temperature based on spatially distributed and averaged parameters. Keywords: AlGaN; FET; GaN; HEMT; thermal current; temperature profile; average temperature 1. Introduction The commercial wireless market requires more demanding microwave operation with higher requirements in terms of self-heating, high operating voltage and inherent processes and their impact on the device reliability in consumer electronics [1–3]. The presence of two-dimensional electron gas (2DEG) in a gallium nitride (GaN) based structure presents the potential to fabricate high electron mobility transistors (HEMTs) with Schottky diodes employed as excellent devices for application in the microwave and power conversion field. The suppression of the critical temperature increase, caused by high power density along the device active area, requires the utilization of high thermal conductance substrates e.g., silicon carbide (SiC) [4]. Since the devices are microscopic in size, the conventional methods lack the accuracy to estimate the device operating temperature. Numerous experimental methods were developed to determine the temperature inside and nearby active device area such as Raman spectroscopy or interferometric map- ping [5–7]. Additionally, various methods utilizing external heating, or a low-power operating regime were employed, taking advantage of specific electro-thermal device prop- erties. However, these methods, that are widely applied to determine average temperature of HEMT operating in the saturation regime, suffer from a lack of accuracy due to the marginalization of the drain current increase caused by, e.g., gate length modulation or leakage effects [8–10]. Moreover, the current comparison at the defined operating point Electronics 2021, 10, 2738. https://doi.org/10.3390/electronics10222738 https://www.mdpi.com/journal/electronics